The present invention relates to a combustion system of an internal combustion engine and, more particularly, to an improvement of a combustion system includes an intake passage and a combustion chamber with two intake valves for improving the combustion efficiency. And, the output efficiency of the entire operation area is improved by the synergetic effect due to generation of the swirl and squish effect in the combustion chamber.
In a conventional technique for this technical field, there has been provided an intake system of an engine of a vehicle for improving the combustion efficiency and the output efficiency by the structure or shape of the combustion chamber.
For example, in order to improve the combustion efficiency, the Japanese Patent Laid-open Publication No. 58-117315 discloses a structure of combustion chamber of an internal combustion engine wherein the curvature of a recessed spherical surface of the combustion chamber on the intake side is made as large as possible so as not to weaken the main intake flow from a helical intake passage.
With the prior art described above, however, the intake flow collides with a plug wall and is thus bent. Accordingly, the energy loss of the intake flow is made large, so that attenuation of a swirl of the intake flow is caused. It is, therefore, difficult to attain effects due to the swirl and squish flow. In particular, the combustion is not stably performed in a low load operation period of the engine. This is a significant problem for the effective combustion of the internal combustion engine.